Field of the Invention
The present invention relates generally to the field of antennas. More specifically, the present invention discloses a dish antenna with a self-supporting sub-reflector assembly suitable for use in satellite broadcasting.
Statement of the Problem
Parabolic reflector antennas are widely used in the field of satellite television broadcasting. With the improvements in receiving/transmitting equipment used on the satellites, more powerful beams are transmitted to the ground and that in turn allows the use of smaller antennas than those used before. Dual-reflector antennas occupy less volume and are preferable for use in mobile applications, such as on recreational vehicles, automobiles, small boats, or in portable antenna systems.
Many dual-reflector antennas have a primary reflector with a generally parabolic shape and a smaller sub-reflector positioned in the focal region of the primary reflector. A waveguide horn extends from the primary reflector toward the sub-reflector.
Accurate positioning of the sub-reflector with respect to the primary reflector and the waveguide horn is a major concern to ensure optimal performance of the antenna. The antenna assembly can be subject to a variety of physical forces in the field, such as wind loads, vibration and mechanical shock, that can adversely affect the positioning and relative alignment of these components. Therefore, a need exists to ensure that the mechanical structure of the reflectors and waveguide horn is relatively sturdy and robust. In addition, the cost of the required components and their simplicity of assembly during the manufacturing process is another major concern, while providing accurate initial alignment of these components. Thus, there remains a need for a dual-reflector antenna that can be easily manufactured and provides a sturdy mechanical structure to maintain proper alignment of the reflectors and waveguide horn.
The prior art in this field includes a number of dual-reflector antennas that use a dielectric tube or other member to support the sub-reflector, including U.S. Pat. No. 3,530,480 (Rongved et al.), U.S. Pat. No. 3,611,391 (Bartlett), U.S. Pat. No. 6,862,000 (Desargant et al.), U.S. Pat. No. 4,673,945 (Syrigos), and U.S. Pat. Nos. 6,137,449, 4,963,878 and 6,020,859 (Kildal). However, none of these references teach or suggest the specific structure of the present invention, in which an insert is used to secure the distal end of a dielectric tube to the sub-reflector.